1. Field of the Invention
The present invention relates to an inkjet recording device, and in particular relates to an inkjet recording device capable of detecting obstacles such as wrinkles and foreign particles on a recording medium.
2. Description of the Related Art
Conventionally, with an inkjet recording device which performs recording by ejecting ink to a recording medium, after printing paper or the like, which is the recording medium, is mounted on a platen, a feed mechanism for feeding the platen feeds such printing paper to the position of an inkjet head. Then, inks are guided from an ink supply source to a plurality of ejection channels of the inkjet head, an actuator such as a heater element or piezoelectric element is selectively driven, and inks are ejected from the nozzle face provided to the tip of the ejection channel to the printing paper or the like. After the recording to the printing paper or the like is completed, the printing paper subjected to recording is returned to the original standby position of the platen before the start of recording.
With this kind of inkjet recording device, when obstacles such as a foreign particle or dust are adhered to the recording medium mounted on the platen, it is known that adverse effects are exerted on the recording results to the recording medium such as the ejection of ink to an accurate position being hindered, or the ink being ejected on such foreign particle or dust and therefore not being attached directly on the recording medium. Further, when these obstacles contact the nozzle face of the inkjet head as a result of the platen being fed, there is a problem in that an adverse effect is exerted on the subsequent printing as a result of the nozzle face being damaged or tainted.
Thus, conventionally, an optical sensor for detecting obstacles such as a foreign particle or dust has been provided to the inkjet recording device. For instance, as the inkjet recording device having such an optical sensor, known is an inkjet recording device in which a printing head in which a plurality of nozzles are disposed serially is passed through above an optical beam, and, when a foreign particle is adhered to the printing head, since the intensity of the optical signal detected with the optical sensor will weaken, the foreign particle adhered to the lower face of the printing head can be detected (for example, c.f. Japanese Patent Application Laid-Open No. H11-179934).
Further, with this kind of inkjet recording device, although it is common practice to perform recording on paper or the like as the recording medium, also known is an inkjet printer for fabrics wherein recording is performed on fabrics such as a T-shirt. With this kind of inkjet printer for fabric, in addition to the problem of the adhesion of obstacles such as foreign particles and dust, there is a problem in that an adverse effect is exerted on the recording results or the nozzle face since the fabric itself, which is the recording medium, easily floats and wrinkles, and the floating and wrinkling of such fabric will become an obstacle.
Thus, known is an inkjet printing device in which a sensor for measuring the distance to the fabric, which is the recording medium, is provided to the side that is more upstream than the printer head at the lower part of the carriage, whereby this sensor continuously measures clearances between the sensor and the fabric surface, and, when the sensor detects clearances of a certain value or less, this detection result is interpreted to indicate a wrinkle, and this is notified to the operator, or the feeding is automatically stopped (for example, c.f. Japanese Patent Application Laid-Open No. 2001-262459).
Nevertheless, with the method of detecting obstacles such as a foreign particle or dust in the inkjet recording device with an optical sensor, depending on the various conditions such as the reflection of the optical beam, there are cases where an obstacle is erroneously detected, or the obstacle cannot be detected, and there is a problem in that the inkjet recording device will malfunction in such a case. Although it is considered to technically advance the optical sensor to deal with the foregoing situation, there is a problem in that the installation of a more accurate optical sensor in an inkjet recording device will cause increased costs.
Moreover, even with the invention described in Japanese Patent Application Laid-Open No. 2001-262459, since it employs an optical sensor to measure the clearance between the sensor and the fabric surface, it encounters the same problem as with the conventional method described above.
Meanwhile, after the recording to the recording medium is completed, with an inkjet recording device which feeds the platen to a standby position of the platen before the start of recording, there is a problem in that the recording medium subjected to recording and mounted on the platen contacts the optical sensor upon passing though immediately beneath the optical sensor due to the thickness of the ejected ink or the floating or wrinkling that occurs upon feeding. In particular, when the recording medium contacts the optical sensor in a state in which the ejected ink is not yet completely dried, the optical sensor will become tainted with the ink ejected on the recording medium, and there is a problem in that the precision of the optical sensor will deteriorate. Meanwhile, also with the recording medium subjected to recording, there is a problem in that the ink would smear or taint the recording medium or the optical sensor as a result of contacting the optical sensor. Further, there is also a possibility that the contact of the optical sensor and recording medium would damage each other.